A single class of proteins - the ion channels - is the major determinant of neuronal signaling properties, and a long-term objective of this laboratory is to determine the contributions made by individual classes of ion channel to the signaling properties of neurons. Our current focus is on a family of K+ channels, the Ca2+-activated potassium channels because 1) they are found in virtually all neurons and also in many non-neuronal cells, 2) they play numerous functional roles in these various cell types, and 3) the properties of these channels varies in different cellular contexts due to the association of hetero-tetramers, alternative splicing, association with other accessory proteins, and modulation by second messenger cascades. Our specific aims are: 1) Identify and characterize candidate association and tetramerization domains in KCa channels. We will test the hypothesis that KCa channels contain specific protein domains that facilitate the tetramerization of some, and exclusion of other subunits. 2) Identify and characterize intermolecular KCa channel association domains and the resulting protein complexes. We will test the hypothesis that KCa channel a-subunits contain protein domains facilitating the intermolecular binding of other proteins to KCa channel tetramers resulting in novel Kca channel phenotypes. 3) Determine the role of alternative splicing of KCa channel a-subunits on protein complex formation. We will test the hypothesis that splice variants contain specific recognition domains for subsets of Kca channel binding proteins. 4) Determine the role of protein phosphorylation in modulating the identity and functionality of ion channel complexes. We will test the hypothesis that protein phosphorylation can dynamically rearrange the makeup of ion channel complexes, and hence alter the functionality of KCa channels within these complexes